Effort reducing start mechanism for hydraulically propelled vehicles

ABSTRACT

A propulsion unit  10 , used to propel a line striper, is provided with a gasoline engine  12  which may have either a pull/recoil or an electrical starter. Engine  12  is connected via a centrifugal clutch  14  of a known type to a hydraulic pump  16  which includes a hydrostatic drive unit  18 . In the preferred embodiment, the clutch  14  is designed to engage between the cranking speed and the idle speed.

TECHNICAL FIELD

This application claims the benefit of U.S. application Ser. No.61/015,057, filed Dec. 19, 2007, the contents of which are herebyincorporated by reference.

BACKGROUND ART

Line striper propulsion units are well known such as those sold underthe LINEDRIVER trademark by the assignee of the instant invention. Insuch units, a gasoline engine directly drives a hydraulic pump thatsupplies a hydrostatic drive system. While such units work well fortheir intended use, when used in colder temperatures, the engine is hardto start because the high viscosity of the hydraulic fluid at lowertemperatures makes it hard to (pull or electrically) start the engine.

DISCLOSURE OF THE INVENTION

A centrifugal clutch of a known type is placed between the engine andthe hydraulic pump. In the broader sense of the invention, the clutch isdesigned to engage just above the engine's idle speed. In the preferredembodiment, the clutch is designed to engage between the cranking(recoil or electric) speed and the idle speed. In this preferredembodiment, once the engine catches, the clutch will be engaged to thatthere will be no engagement or disengagement during normal operation.

These and other objects and advantages of the invention will appear morefully from the following description made in conjunction with theaccompanying drawings wherein like reference characters refer to thesame or similar parts throughout the several views.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the engine-clutch-pump combination of the instantinvention.

FIG. 2 shows a schematic layout of a propulsion unit.

BEST MODE FOR CARRYING OUT THE INVENTION

A propulsion unit, such as would be used to propel a line striper, isgenerally designated 10 and is provided with a gasoline engine 12 whichmay have either a pull/recoil or an electrical starter. Engine 12 isconnected via a centrifugal clutch 14 of known type to a hydraulic pump16 which includes a hydrostatic drive unit 18 which is in turn connectedto wheel motors 20. In the preferred embodiment, the clutch 14 isdesigned to engage between the cranking (recoil or electric) speed andthe idle speed. By way of example, the cranking speed may be 600 rpm,the engagement speed 830 rpm and the idle speed 1440 rpm. In thispreferred embodiment, once the engine catches, the clutch will beengaged to that there will be no engagement or disengagement duringnormal operation.

It is contemplated that various changes and modifications may be made tothe propulsion unit without departing from the spirit and scope of theinvention as defined by the following claims.

1. In a propulsion unit having a gas engine, a hydraulic pump driven bysaid gas engine and a hydrostatic drive, the improvement comprising acentrifugal clutch being driven by said engine and driving saidhydraulic pump.
 2. The propulsion unit of claim 1 wherein said enginehas an idle speed and centrifugal clutch engages above said idle speed.3. The propulsion unit of claim 1 wherein said engine has an idle speedand a cranking speed and centrifugal clutch engages between said idlespeed and said cranking speed.